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We have included the description from the NetLogo Urban Suite where this model is located as it is rather convoluted an explanation and this text below is a better explanation than my own.
This model simulates points of information and/or resource exchange in an urban environment. An urban environment is assumed to be a pedestrian friendly city-space where people normally encounter one another on a face-to-face basis; and, typically encounter informational systems (such as advertising) and exchange systems (such as consumer based shopping).
The object of the model is to simulate people's awareness of the value of exchanging resources, and evaluate the influence "aware" people have on one another, and on their environment in an information-rich context such as a city.
The model determines a person's theoretical level of "awareness" within an urban environment based upon a person's random encounter with information centers. In the model, information centers are any source of positive information exchange such as an advertisement (for a public good) or a recycling center. In general terms, "awareness" involves a person showing realization, perception, or knowledge.
In this model, each person has some amount of "awareness", which is measured in "awareness points". There is a discrete set of "levels" of awareness that people may attain. A person may be "unaware" (0 - 5 points), "aware" (5 - 10 points), "well-informed" (10 - 15 points), or an "activist" (more than 15 points).
To gain awareness, a person either runs into a center, where they gain five awareness points; or is influenced by a person who is well-informed or an activist, where they gain one awareness point. If one of these events does not occur during a given time step (tick), the person will lose one awareness point (down to zero). In this model, there is no such thing as "negative awareness".
(The idea of negative awareness may sound ridiculous, but it could make sense in some situations -- for instance, if some faction is spreading information that is in direct conflict to another faction, and people may come into contact with information and advertising promoting either position. That is, negative awareness might represent "subscription to an opposing and irreconcilable viewpoint". For instance, in the United States, there are activists working both for and against the legality of abortion.)
When a person becomes an activist (15 awareness points), a new center is formed. The new information centers are colored blue, whereas the initial information centers are green.
If no one comes into contact with a center for a specified amount of time (see the NON-USAGE-LIMIT slider), the center disappears from the world. The intuition here is that if an information/advertising method or location is yielding no fruit, eventually it will be shut down.
Press SETUP and then GO.
The PEOPLE slider determines how many people "agents" are randomly distributed in the initial setup phase of the model
The CENTERS slider determines how many information centers are randomly distributed in the initial setup of the model.
The NON-USAGE-LIMIT determines how many ticks a center can go unused before being shut down.
Use the PLACE-CENTERS button to manually place information centers on the view (by clicking their locations with the mouse, while the PLACE-CENTERS button is turned on).
There are also numerous monitors that display information about the current state of the world, such as the current breakdown of awareness in the population, via the ACTIVIST, "WELL INFORMED", AWARE, and UNAWARE monitors.
The CENTERS monitor tells how many information centers are present in the world.
The AVG. NON-USAGE monitor tells the average number of ticks it has been since each of the information centers has been used (i.e. influenced a person).
The AVERAGE STATE OF AWARENESS monitor tells the average number of awareness points that people in the population have.
The LEVELS OF AWARENESS plot shows the history of how many people were at each level of awareness at each tick of the model, and the AVG. AWARENESS plot keeps track of the average awareness of the population over time.
The initial relative density of people to centers is vital to achieving systemic balance. The model simulates a complex system of data exchange by exploring positive feedback; and the model was created as a lens to describe one important process of emergent pattern formation in a sustainable city. Specifically, the model allows us to study and discuss the important relationship between a population and its ability to learn and become participatory in the building of its own environment. Here are some questions to encourage discussion about the model and the topics it broaches.
Is there a minimum number of people or centers needed to eventually make everyone an activist? Does it happen suddenly or gradually? You can see this both visually, and it is represented in both the LEVELS OF AWARENESS plot, and the AVG. AWARENESS plot.
Where do new information centers tend to form?
What if you only look at the number of "aware" or "well-informed" people over time -- what does that plot look like? Can you explain its shape?
Run the model with 200 PEOPLE, 50 CENTERS, and 100 ticks for the NON-USAGE-LIMIT. Now try decreasing the NON-USAGE-LIMIT slider. How low can you go before global awareness isn't achieved? Does it help to raise the initial number of people or centers?
Try manually placing 20 centers (using the PLACE-CENTERS button) spread out across the world, and run the model. Now try manually placing just 5 centers, but in a tight cluster. What are the results? Do you think this result is realistic, or is indicative of a faulty model of how awareness and activism occurs?
Try changing the model so that it simulates two competing and opposed viewpoints (such as legalizing marijuana, or perhaps something more broad, such as Republican versus Democrat politics). Do this by allowing negative awareness, and have people with less than -15 awareness points be anti-activists, etc.
What if there were more than two opposing points of view?
It is very common in agent-based models to initialize the setup of the model by positioning agents randomly in the world. NetLogo makes it easy to move an agent to a random location, with the following code: "SETXY RANDOM-XCOR RANDOM-YCOR".
This model is related to all of the other models in the "Urban Suite".
This model is also similar to the Rumor Mill model, which is found in the NetLogo models library.
The original version of this model was developed during the Sprawl/Swarm Class at Illinois Institute of Technology in Fall 2006 under the supervision of Sarah Dunn and Martin Felsen, by the following students: Eileen Pedersen, Brian Reif, and Susana Odriozola. See http://www.sprawlcity.us/ for more information about this course.
Further modifications and refinements were made by members of the Center for Connected Learning and Computer-Based Modeling before releasing it as an Urban Suite model.
The Urban Suite models were developed as part of the Procedural Modeling of Cities project, under the sponsorship of NSF ITR award 0326542, Electronic Arts & Maxis.
Please see the project web site ( http://ccl.northwestern.edu/cities/ ) for more information.